U.S. patent number 4,916,262 [Application Number 07/266,749] was granted by the patent office on 1990-04-10 for low-profile, rubber keypad.
This patent grant is currently assigned to Motorola, Inc.. Invention is credited to Scott D. Beutler, Polly S. Jungels-Butler.
United States Patent |
4,916,262 |
Jungels-Butler , et
al. |
April 10, 1990 |
**Please see images for:
( Certificate of Correction ) ** |
Low-profile, rubber keypad
Abstract
A low-profile rubber keypad with good tactile feel and
illuminability includes a plurality of layers adhesively bonded to
one another. The top layer of the keypad is a silicone rubber
overlay having a plurality of keys protruding therefrom. The rubber
overlay is adhesively bonded to an actuation layer including a
plurality of thin actuating strips. The actuation layer is
adhesively bonded to a tactile layer including a plurality of
collapsible resilient domes. The tactile layer is adhesively bonded
to a shorting layer including a plurality of conductors. The
shorting layer is adhesively bonded to a flex circuit layer
including a plurality of conductors.
Inventors: |
Jungels-Butler; Polly S.
(Streamwood, IL), Beutler; Scott D. (Hoffman Estates,
IL) |
Assignee: |
Motorola, Inc. (Schaumburg,
IL)
|
Family
ID: |
23015844 |
Appl.
No.: |
07/266,749 |
Filed: |
November 3, 1988 |
Current U.S.
Class: |
200/5A; 200/306;
200/514; 200/515; 200/517 |
Current CPC
Class: |
H01H
13/702 (20130101); H01H 13/703 (20130101); H01H
2203/052 (20130101); H01H 2209/038 (20130101); H01H
2209/06 (20130101); H01H 2209/082 (20130101); H01H
2211/004 (20130101); H01H 2213/002 (20130101); H01H
2213/014 (20130101); H01H 2213/016 (20130101); H01H
2215/006 (20130101); H01H 2215/048 (20130101); H01H
2217/016 (20130101); H01H 2219/056 (20130101); H01H
2223/022 (20130101); H01H 2227/002 (20130101); H01H
2231/022 (20130101); H01H 2239/034 (20130101) |
Current International
Class: |
H01H
13/702 (20060101); H01H 13/70 (20060101); H01H
013/70 () |
Field of
Search: |
;200/5R,5A,86R,159B,306,340,DIG.1,512,513,515,517,600 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; J. R.
Attorney, Agent or Firm: Hackbart; Rolland R.
Claims
We claim:
1. A keypad comprising in combination:
a rubber overlay having a top surface with a plurality of
protruding portions producing keys, and having a substantially flat
bottom surface;
a first adhesive layer having an outer edge portion bonded to the
bottom surface of the rubber overlay at the periphery thereof;
an actuation layer having a top surface bonded by the first
adhesive layer to the rubber overlay, having a bottom surface, and
having a plurality of pairs of cavities each separated by an
actuating strip thereof, each actuating strip being substantially
aligned with a corresponding key;
a second adhesive layer having an outer edge portion bonded to the
bottom surface of the actuation layer at the periphery thereof;
a tactile layer having a top surface bonded by the second adhesive
layer to the actuation layer, having a bottom surface, and having a
plurality of collapsible resilient domes, each dome being
substantially aligned with a corresponding actuation layer and
key;
a third adhesive layer having a plurality of cavities each
substantially aligned with a corresponding key and being bonded to
the bottom surface of the tactile layer;
a shorting layer having a top surface bonded by the third adhesive
layer to the tactile layer, having a bottom surface, and having a
plurality of conductive areas thereon, each conductive area being
substantially aligned with a corresponding key; and
a fourth adhesive layer having a plurality of cavities each
substantially aligned with a corresponding key and being bonded to
the bottom surface of the shorting layer;
a circuitry layer having a top surface bonded by the fourth
adhesive layer to the shorting layer, having a bottom surface, and
having a plurality of conductor pairs, each conductor pair being
substantially aligned with a corresponding conductive area of said
shorting layer, whereby depression of a key and corresponding
actuating strip collapses a corresponding dome to produce contact
between a corresponding conductive area and a conductor pair.
2. The keypad according to claim 1, wherein said first adhesive
layer further includes a plurality of pairs of cavities each
separated by an actuating strip thereof, each actuating strip of
the first adhesive layer being substantially aligned with an
actuating strip of the actuation layer.
3. The keypad according to claim 1, wherein said circuitry layer is
adhesive backed.
4. The keypad according to claim 1, wherein said tactile layer,
shorting layer and circuitry layer each further include at least
one venting hole which intersect and interconnect air passages of
said third and fourth adhesive layers.
5. A keypad adapted to be surface mounted to a substrate,
comprising:
a rubber overlay having a top surface with a plurality of
protruding portions producing keys, and having a substantially flat
bottom surface;
a first adhesive layer having an outer edge portion bonded to the
bottom surface of the rubber overlay at the periphery thereof;
an actuation layer having a top surface bonded by the first
adhesive layer to the rubber overlay, having a bottom surface, and
having a plurality of pairs of cavities each separated by an
actuating strip thereof, each actuating strip being substantially
aligned with a corresponding key;
a second adhesive layer having an outer edge portion bonded to the
bottom surface of the actuation layer at the periphery thereof;
a tactile layer having a top surface bonded by the second adhesive
layer to the actuation layer, having a bottom surface, and having a
plurality of collapsible resilient domes, each dome being
substantially aligned with a corresponding actuation layer and
key;
a third adhesive layer having a plurality of cavities each
substantially aligned with a corresponding key and being bonded to
the bottom surface of the tactile layer;
a shorting layer having a top surface bonded by the third adhesive
layer to the tactile layer, having a bottom surface, and having a
plurality of conductive areas thereon, each conductive area being
substantially aligned with a corresponding key;
a fourth adhesive layer having a plurality of cavities each
substantially aligned with a corresponding key and being bonded to
the bottom surface of the shorting layer;
a circuitry layer having a top surface bonded by the fourth
adhesive layer to the shorting layer, having a bottom surface, and
having a plurality of conductor pairs, each conductor pair being
substantially aligned with a corresponding conductive area of said
shorting layer, whereby depression of a key and corresponding
actuating strip collapses a corresponding dome to produce contact
between a corresponding conductive area and conductor pair; and
a fifth adhesive layer bonded to the bottom surface of the
circuitry layer for bonding said circuitry layer to the
substrate.
6. The keypad according to claim 5, wherein said first adhesive
layer further includes a plurality of pairs of cavities each
separated by an actuating strip thereof, each actuating strip of
the first adhesive layer being substantially aligned with an
actuating strip of the actuation layer.
7. The keyboard according to claim 5, wherein said tactile layer,
shorting layer and circuitry layer each further include at least
one venting hole which intersect and interconnect air passages said
third and fourth adhesive layers.
Description
BACKGROUND OF THE INVENTION
The present invention is generally related to telephone keypads and
more particularly to an improved low-profile, rubber keypad for use
in cellular portable telephones.
Prior art low-profile keypads are available that have good tactile
feedback but typically do not allow back illumination through the
interconnect and switching circuitry. In order to provide for back
illumination and good tactile feedback, a high-profile keypad
incorporating plunger type actuator keys or self-tactile rubber
keypads is required. Back illumination through such high-profile
keypads is not possible since the keys incorporate a carbon
conductor or a metallic popple, both of which are opaque. This
problem has been solved in part by using a separate lightpipe (see
U.S. Pat. No. 4,124,879) or a thick rubber pad as a lightpipe (see
U.S. Pat. No. 4,636,593) to distribute the required illumination to
the keys of the keypad. For the foregoing reasons, there is a need
for an improved low-profile keypad that has good tactile feedback
and back illuminability.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
improved low-profile rubber keypad with good tactile feedback and
back illuminability.
It is another object of the present invention to provide an
improved low-profile rubber keypad that has a floating rubber
overlay with protruding keys.
It is yet a further object of the present invention to provide an
improved low-profile rubber keypad that has an adhesive backing for
surface mounting thereof as a component.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of a low-profile rubber
keypad embodying the present invention.
FIG. 2 is a partial cross-sectional view of the low-profile rubber
keypad in FIG. 1 taken along lines 2--2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, there is illustrated an exploded perspective view of a
low-profile rubber keypad 100 embodying the present invention.
Keypad 100 may be advantageously utilized in a cellular portable
telephone as the user entry device. According to a feature of the
present invention, keypad 100 is adhesive backed to facilitate
mounting on a surface of the cellular portable telephone.
Referring to FIG. 2, there is illustrated a partial cross-sectional
view of a single key 130 of the low-profile rubber keypad 100 in
FIG. 1 taken along lines A-A. In the preferred embodiment, keypad
100 includes a plurality of layers 102-120 which are adhesively
attached to one another. All layers 102-120 of keypad 100 have been
designed to be clear or translucent such that rubber overlay 102
may be back illuminated form a light source by means of diffuser
plate 122.
Referring to FIGS. 1 and 2, the top layer of keypad 100 is a
silicone rubber overlay 102 having a top surface with a plurality
of protruding keys and a flat bottom surface. Other materials may
be used for overlay 102, such as, for example, an embossed
polyester sheet for reduction in the thickness of keypad 100.
Rubber overlay includes a 0.030 inch thick flat backing with 0.015
inch thick protruding keys molded thereto (overall thickness of
0.045 inch). Rubber overlay 102 is bonded to actuation layer 106 by
a 0.002 inch thick silicone rubber adhesive layer 104, which has
the same physical configuration as the actuation layer 106.
Actuation layer 106 is 0.005 inch thick and comprised of a die-cut
polyester sheet which has been formed such that thin actuating
strips 140, approximately 0.060 inch wide will lay over the top of
each embossed dome 132 on the tactile layer 110. Actuation layer
106 is bonded to the tactile layer 110 at the periphery thereof and
in an area that separates the two sizes of keys on rubber overlay
102. The thickness of adhesive layer 108 is 0.007 inches. The
required thickness for rubber overlay 102 with good tactile feel is
reduced by using actuating strips 140 over the embossed polyester
domes 132.
Tactile layer 110 of keypad 100 includes a plurality of collapsible
resilient domes 132 each opposite a corresponding key 130 and is
bonded to the shorting layer 114 by adhesive layer 112
substantially over their entire adjacent surfaces except for areas
corresponding to each dome 132. The thickness of adhesive layer 112
is 0.007 inches. Shorting layer 114 includes on its bottom surface
a plurality of conductors 134 (shown in dashed lines in FIG. 1)
substantially opposite corresponding keys 130 and is bonded to flex
circuit layer 118 by adhesive layer 116 substantially over their
entire adjacent surfaces except for areas corresponding to each
dome 132 of tactile layer 110. Adhesive layer 116 is identical to
adhesive layer 112. Flex circuit layer 118 includes on its top
surface a plurality of conductors 136 (see representative
conductors pair shown in FIG. 1) substantially opposite
corresponding conductors 134 and is bonded to double-sided adhesive
layer 120 substantially over their entire adjacent surfaces for
attaching keypad 100 to a substrate, such as, for example, the
cellular telephone housing or a circuit board. In the preferred
embodiment, keypad 100 is attached to a diffuser plate 122 coupled
to a light source for back illuminating keys 130.
The operation of keypad 100 occurs when the operator's finger
depresses a rubber key 130. The force from the operator's finger is
effectively concentrated on actuating strip 140 of the actuation
layer 106 beneath the key 130. The actuating strip 140 depresses a
corresponding dome 132 on tactile layer 110. Dome 132 on the
tactile layer 110 then collapses which results in a switch closure,
i.e. electrical continuity between conductors 136 on flex circuit
layer 118 by way of one or more conductors 134 on shorting layer
114. The configuration of adhesive layers 104, 108, 112 and 116
prevents early contact between conductors 134 and 136, excessive
preload of polyester domes 132, and together with holes 150 aides
in the venting of air within keypad 100.
According to a feature of the present invention, rubber overlay
102, adhesive layer 104 and actuation layer 106 essentially float
above tactile layer 110 since adhesive layer 108 is disposed
between actuation layer 106 and tactile layer 110 only at the
perimeter of keypad 100 and between the two sizes of keys 130. By
floating rubber overlay 102, adhesive layer 104 and actuation layer
106, the air volume between actuation layer 106 and tactile layer
110 does not unduely increase the force necessary to depress keys
130. The tactile feel of keys 130 and the air volume between
actuation layer 106 and tactile layer 110 is further controlled by
means of holes 150. Hole 150 intersect the air passages e.g. 160
and 162 in adhesive layers 112 and 116. One hole 150 has been
provided for each of the rows of keys 130, which are interconnected
by corresponding air passages e.g. 160 and 162 in adhesive layers
112 and 116. In the preferred embodiment, four holes 150 are used
for the larger twelve digits, and two holes 150 are used for the
smaller eight function keys.
The backlighting of keypad 100 occurs when light from diffuser
plate 122 washes the back of flex circuit layer 118. Since all
layers 102-120 are clear or translucent, light from diffuser plate
is dispersed throughout keypad 100. Conductors 134 on flex circuit
layer 118 and the conductors 136 on shorting layer 114 are gold and
silver, respectively. Conductors 134 and 136 are relatively thin
(0.03 mm in width) and separated by a space approximately twice
their width. Conductors 136 on flex circuit layer 118 are arranged
perpendicular to conductors 134 on shorting layer 114. The
resulting cross-hatch pattern of conductors 134 and 136 causes good
light dispersion. The light from diffuser plate 122 is further
scattered by the embossed tactile domes 132.
Applications of keypad 100 in harsh environments are limited
primarily by the environmental characteristics of embossed
polyester domes 132 on tactile layer 110. In the preferred
embodiment, embossed polyester domes 132 are capable of
withstanding 85 degrees Centrigrade and 85-90% relative humidity
for a minimum of 130 hours. Domes 132 and thus keypad 100 can also
withstand thermal shock cycling of -40 degrees Centrigrade to +85
degrees Centrigrade. If keypad 100 is vented into a water and dust
resistant housing, keypad 100 will likewise be water and dust
resistant. Keypad 100 is expected to have a lifetime of at least
one million actuations minimum.
In summary, a unique low-profile multi-layer rubber keypad has been
described which has good tactile feedback and back illuminability.
Tactile feedback of the keypad is enhanced by floating the rubber
overlay on which protruding keys are formed. The novel keypad is
back illuminated through the layers thereof including the
intervening switching and circuitry layers. The keypad of the
present invention may be advantageously utilized in any
applications where small size, backlighting, and good tactile feel
are desired.
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